Pyridoxine supplementation during oocyte maturation improves the development and quality of bovine preimplantation embryos

- We investigated the effect of pyridoxine during IVM on the developmental competence of bovine oocytes.
- Supplementation of pyridoxine during IVM significantly decreased the activity of CTSB in bovine COCs.
- Pyridoxine improved the developmental competence of bovine oocytes by increasing the blastocyst rate.
- Pyridoxine improved the quality of the produced embryos by increasing the TCN and decreasing the apoptotic rate.
- Therefore, pyridoxine is a promising tool to improve the developmental competence of bovine oocytes and embryo quality.

Recently, inhibition of cathepsin B (CTSB) activity during in vitro maturation (IVM) and culture (IVC) improved the developmental competence and quality of bovine oocytes and embryos. E-64 is a widely used inhibitor to inhibit CTSB activity, however, E-64 inhibits not only CTSB activity but also the activities of other proteases including cathepsin L (CTSL), papain, calpain, and trypsin. Pyridoxine, the catalytically active form of vitamin B6, plays a crucial role in several cellular processes and has the ability to inhibit CTSB activity. However, whether pyridoxine has an improving effect during IVM of bovine oocytes is still unknown. In this study, we investigated the effect of pyridoxine supplementation during IVM on the developmental competence of bovine oocytes and the quality of the produced blastocysts. Supplementation of pyridoxine to the maturation medium significantly decreased the activity of CTSB in both bovine cumulus cells and oocytes. Moreover, pyridoxine improved both the blastocyst and hatched blastocyst rates. In addition, the presence of pyridoxine during IVM also significantly improved the quality of the produced embryos by increasing the total cell number as well as decreasing the CTSB mRNA expression and apoptotic rate. These results indicate that pyridoxine is a promising tool to improve the developmental competence of bovine oocytes and subsequent embryo quality.